A common problem with companies who provide their employees with mobile (cellular) telephones is to restrict usage of the telephone for business purposes. This is an added problem if the taxation system discriminates between the use of the phone for business and for domestic purposes. Although it is possible to track calls from the computer printout of charged calls, good staff working relations may be lost if they are disciplined for unauthorized calls. It is considered likely that many more companies would use mobile telecommunication networks and permit more employees to have mobile telephones if their use could be limited to company business and the costs more tightly controlled. Additionally, organisations providing a motorist service, such as a breakdown service, may offer limited-use telephones for their customers to call them and possibly a few other telephone numbers, such as the police, their home and their work numbers.
The present invention seeks to provide a telephone instrument and a system for enabling only authorized calls to be made from mobile telephone instruments according to a preprogrammable repertory of authorized calls. The repertory of authorized calls is preset only by a licensed person or by the manufacturer so that the mobile telephone may be used only to call one or more authorized numbers. The number of preprogrammed calls which can be made will depend upon the particular needs of each company and each individual employee or user. However it is unlikely that more than 20 preset authorized numbers/keys would be made available and some instruments will have only one preset authorized number/key.